Aircraft propulsion system comprising an AFT pylon fairing with lateral walls that are profiled for injecting cool air along a thermal protection floor

Abstract

The invention proposes to protect a rear part of a floor of an aft fairing of a pylon of an aircraft bypass turbojet engine using a film of cool air formed of part of a bypass flow of the jet engine which is guided under the floor by two lateral wall portions of this fairing which have been profiled for this purpose. To do that, these two lateral wall portions delimit respective air passage spaces formed between a forward part of the floor and a jetpipe of the turbojet engine and which open laterally and towards the rear.

The invention claimed is: 
     
       1. A propulsion system for an aircraft, the propulsion system comprising:
 a bypass turbojet engine; and 
 a pylon for attaching the bypass turbojet engine to an airframe of the aircraft, the pylon comprising an aft fairing comprising two lateral walls, a floor to protect the pylon from a heat of a primary flow ducted by a jetpipe of the bypass turbojet engine, and, formed in each of the two lateral walls, a recess in a form of an air passage, wherein each recess is respectively defined by the jetpipe on a bottom of the recess, a lateral floor portion on a top of the recess, and a lateral wall portion on an inner surface of the recess, 
 wherein each lateral floor portion has a surface that curves towards an exterior surface of an ejection bullet, around which the jetpipe extends, 
 wherein the pylon is configured such that a base is disposed between the jetpipe and the two lateral floor portions of the pylon, the base being formed by the lateral wall portion of each of the lateral walls of the aft fairing at an end facing a rear of the propulsion system, and wherein each lateral wall portion is configured to extend towards the rear of the propulsion system and is curved towards a mid-plane of the aft fairing, 
 wherein each lateral floor portion is disposed on either side of the mid-plane of the aft fairing and is separated from the jetpipe so that the lateral floor portions and the lateral wall portions, along with the jetpipe, delimit each air passage, which are open laterally and towards the rear of the propulsion system, and 
 wherein the floor is configured such that at least a part of a bypass stream is injected under the lateral floor portions to form a film of cool air under the floor for protecting the pylon from the heat of the primary flow. 
 
     
     
       2. The propulsion system according to  claim 1 , wherein each lateral wall portion has a convex face facing towards an outside of the aft fairing when the latter is viewed in section on a plane orthogonal to the mid-plane and parallel to an axis of the bypass turbojet engine. 
     
     
       3. The propulsion system according to  claim 1 , wherein a separation between each lateral floor portion and the jetpipe at a rear end of a corresponding lateral wall portion is between 2% and 15% of a maximum width of the aft fairing at a trailing edge of the jetpipe. 
     
     
       4. The propulsion system according to  claim 1 , wherein the jetpipe comprises an extension configured to extend as a projection rearwards and to face the floor of the aft fairing. 
     
     
       5. The propulsion system according to  claim 1 , wherein the two lateral walls of the aft fairing extend, respectively, in a continuation of two fork walls which connect together two annular cowls which, respectively, on an inside and on an outside thereof, delimit an annular space in which the bypass stream flows through the bypass turbojet engine. 
     
     
       6. The propulsion system according to  claim 1 , wherein the floor of the aft fairing comprises a forward part configured to extend in line with the jetpipe to a rear end of the jetpipe and a rear part configured to extend rearwardly from the jetpipe, so as to be substantially continuous with the forward part. 
     
     
       7. An aircraft comprising at least one propulsion system according to  claim 1 .